The goal of this research is to understand the function of calmyrin, a myristoylated calcium-binding protein that interacts with the Alzheimer's disease related protein, presenilin-2 (PS2). Our preliminary data suggest calmyrin is a calcium sensor: calcium binding triggers a large conformational change in the protein. We believe that the calcium-induced change in calmyrin conformation is important for facilitating its dynamic intracellular targeting and binding to proteins, such as PS2. We found overexpression of calmyrin induces calcium dysregulation and apoptosis. However, the mechanism(s) by which calmyrin induces calcium dysregulation and apoptosis is not known. Calmyrin shares highest homology with calcineurin B, the regulatory subunit of protein phosphatase 2B (calcineurin). In a yeast two-hybrid screen, we isolated calmitase, a putative serine phosphatase. Our preliminary results suggest that calmitase might be analogous to calcineurin, in that it could be the catalytic phosphatase component that is regulated by calmyrin. In accord with this hypothesis, we found calmyrin binds calmitase in a calcium-dependent manner and that co-expression of calmyrin and calmitase results in a dramatic alteration in calmitase localization in the nucleus and stimulates nuclear import of an NFATc-GFP reporter. We also found that transgenic expression of an MSV-driven calmyrin construct causes alopecia and premature death in mice. We believe that calmyrin is an important protein and propose to use a multi-pronged approach to characterize calmyrin and calmitase functions. We propose four specific aims: Aim 1, to determine the role of calmyrin in cell function. Aim 2, to characterize and determine the function of calmitase. Aim 3, to characterize MSV-calmyrin transgenic mice. Aim 4, to generate mice that are disrupted of the calmyrin gene in specific organs and tissues. The results obtained from the proposed research will lead to a better understanding of calmyrin in cells and organisms, and ultimately, its role in health and disease